The Sand Snakes are the bastard daughters of Prince Oberyn Martell.[1][2] The collective name references the Dornish bastard surname, Sand, and their father's nickname, the Red Viper. Oberyn's eight daughters have been born to five different mothers.[3] While they differ in appearance, they are said to all have their father's eyes in shape if not in color.[1]

Quotes

His tourneys, his battles, his duels, his horses, his carnality ... it was said that he bedded men and women both, and had begotten bastard girls all over Dorne. The sand snakes, men called his daughters. So far as Tyrion had heard, Prince Oberyn had never fathered a son.[8]

Arianne: Are you certain you are not off to some other bed, some other woman? Tell me who she is. I will fight her for you, bare-breasted, knife to knife. Unless she is a Sand Snake. If so, we can share you. I love my cousins well.Arys: You know I have no other woman. Only ... duty.[4]

Arianne loved all her bastard cousins, from prickly, hot-tempered Obara to little Loreza, the youngest, only six years old. Tyene had always been the one she loved the most, though; the sweet sister that she never had.[5]